Some African birds leave the nest later
Males leave only when they have better chances of leading their own group
A STUDY on a desert-dwelling African bird is now yielding some answers as to why some African birds take longer to leave the nest than others.
Researchers from the UCT Institute of African Ornithology, the University of Western Australia, and Capilano University in North Vancouver examined the behaviour of wild southern pied babblers.
The bird species live in family groups of up to 14 in the Kalahari Desert.
The findings of the study, published in the Journal of Animal Ecology, suggest that better prospects elsewhere, as well as family dynamics between brothers and stepfathers play a big part in determining when offspring disperse.
Study lead author and post-doctoral fellow at the University of British Columbia Dr Martha Nelson-Flower said males often left when there was more rain, which probably meant there was more food in the environment.
“They also leave when there are more breeding vacancies for males, and when the distance between groups is small. We think that’s because they’re more likely to encounter other groups, and they can check to see if there are any breeding vacancies in those groups,” said Nelson-Flower.
Their findings were based on 11 years of investigation on how the dispersal of male and female babblers were affected by their position in the group social hierarchy, conditions in the environment, and the benefits of staying in their group.
The study found that males left only when they had improved chances of leading their own group elsewhere, while females lower in the pecking order bided their time and waited for opportunities to overthrow dominant females in other groups.
“However, a male’s position in the group social hierarchy made a big difference to their decision to disperse.
“Brothers queue for an opportunity to inherit the leadership of their group – or that of a neighbouring group – by leaving early, younger brothers could boost their queue position and improve their prospects.
“Intriguingly, males with stepfathers also left early, likely because stepfathers prioritise their own, younger sons in the queue.” said Nelson-Flower.
“A large subordinate strong female would go to a group with a dominant female, and attack that female until she left. Sometimes sisters would come in pairs, and they would work together,” she said.